When I suggested not disconnecting the frequency valve, I meant electrically! Do not disconnect it electrically. Instead disconnect the Oxygen sensor (under the pass side floor mat). The system needs the steady duty-cycle based fuel leak that the frequency valve gives to work properly. The fuel distributor will not work like a simple K-Jet distributor by electrically removing the freq valve. The simple K-jet dist has a preset differential pressure. The K-Jet w/Lambda dist has almost no differential pressure difference without an operating frequency valve. Try disconnecting and driving at any mixture adjustment. It just won't go!
By removing the oxygen sensor you achieve no electronic mixture control.
"If I understand you correctly, if the 10% differential at ALL of these different flow rates cannot be maintained, then the fuel distributor is beyond adjusment? "
Yes. If you measure the flow rates at three different rates (the numbers aren't as important as the relationship between each injector circuit) the relative differences from injector to injector should stay within 10% in each range. It is much more important at idle. Of the three numbers the idle spec of 10cc/minute is the most important.
Bosch Master, ASE Master, L1
33 years MB technician